Ectopic production of peptide growth factors by malignant cells, which are also capable of utilizing them (autocrine stimulation), confers a selective growth advantage to tumor tissues. Epidermal growth factor (EGF)-competing peptides are an example of these ectopic growth factors and sarcoma growth factor (SGF), produced by Moloney sarcoma virus-transformed murine cells, is the best-characterized example of these peptides. SGF accounts, however, for only a small portion (about 10%) of the total EGF-competing activity in serum-free conditioned medium. The majority of the EGF-competing activity is separated as a larger molecular weight species on the initial Bio-Gel P-60 column eluted with 1 M acetic acid. Ion exchange chromatography of these larger species on CM-cellulose at pH 5 reveals three resolvable activities and the highest specific activity fraction from this column is itself heterogeneous when chromatographed by reverse phase high pressure liquid chromatography (HPLC) on a Bondapak C18 column eluted by either acetonitrile or propanol. This indicates that these peptides differ structurally from SGF. Following purification to homogeneity, collaboration with other groups to define the primary and secondary structures of these molecules will permit enumeration of the structures of this whole family of SGF-like molecules. Comparison of these structures will help in defining the conserved regions necessary for both EGF receptor binding and mitogenesis. Equally important, comparison of the structures of the SGF family of peptides will indicate whether there is a single "SGF gene" (with peptides related to diferent initiation or termination codons), or whether there is a family of such genes in the murine cells which are activated following Moloney sarcoma virus transformation. To facilitate large-scale production of these EGF-competing growth factors, a variant of the parental cell line is being isolated which is capable of anchorage-independent growth in serum-free medium. Such a variant is currently being characterized for the continued production of these, and perhaps new, ectopic growth factors.